Q. Given the function y=−2(8x2−9x−3)4, find dxdy in any form.Answer: dxdy=
Identify function type and rule: Identify the type of function and the rule needed to differentiate it. The function y=−2(8x2−9x−3)4 is a composite function, where an inner function (8x2−9x−3) is raised to a power and then multiplied by a constant. To differentiate this function, we will use the chain rule.
Apply chain rule: Apply the chain rule. The chain rule states that the derivative of a composite function is the derivative of the outer function evaluated at the inner function times the derivative of the inner function. Let u=8x2−9x−3, so y=−2u4. The derivative of y with respect to u is dudy=−2×4u3=−8u3. Now we need to find dxdu.
Find dxdu: Differentiate the inner function u=8x2−9x−3 with respect to x. The derivative of u with respect to x is dxdu=16x−9.
Substitute into chain rule: Substitute dxdu into the chain rule formula. We have dudy=−8u3 and dxdu=16x−9, so the derivative of y with respect to x is dxdy=dudy⋅dxdu=−8u3⋅(16x−9).
Replace u for final expression: Replace u with the original inner function to get the final expression for dxdy. Substituting u back into the expression, we get dxdy=−8(8x2−9x−3)3⋅(16x−9).
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